bluetooth icon not flashing on low battery!

I have several Macs, etc., but both my iMacs running Mountain Lion have STOPPED flashing the Bluetooth icon to indicate low battery. It is very annoying as I have no way or realizing the batteries are low without constantly checking.

Does anyone know if this is some quirk from the last upgrade?????

Or how to "turn it on" to make it show the batteries are low?

Thanks!